Question

I need help with Part B. I believe that part A is correct.

4.

a) You also wish to synthesize a degenerate oligonucleotide primer that could be used eventually to clone DNA that encodes your mutant protein. Design this degenerate oligo, keeping in mind the rules we talked about in class. More information about designing degenerate primers and primers in general are located on the following page.

Write out the sequence of this oligo here based on this amino acid sequence (Met Ala Pro Met Val Ala Glu):

My answer (Is it correct?)

I got:

5’ AUG - (GCU/C/A/G) - (CCU/C/A/G) - (AUG) - (GUU/C/A/G) - (GCU/C/A/G) - (GAA/G) ‘3

3’ UAC - (CGA/G/U/C) - (GGA/G/U/C) - (UAC) - (CAA/G/U/C) - (CGA/G/U/C) - (CUU/C) 5’

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(What I actually need help with and have no idea where to begin. Please help me)

b) If you synthesized the above oligonucleotide primer, how many different oligos would be present in the mixture?

Follow these rules Modified from the Thermo Fisher web site:

Designing degenerate primers:

Write out your amino acid sequence, label amino and carboxy termini

For each amino acid, use the genetic code to predict the various nucleic acid codons that can encode this amino acid. For all but Met, you should have redundancy present.

Now you need think about 5’ and 3’ considerations, and keep in mind that DNA within genes is double-stranded. It is helpful to keep in mind that the 5’ end of a gene corresponds to the amino terminus of a protein. Using 5’ and 3’ labels write out a single strand DNA sequence corresponding to the your amino seq of interest. You may choose to start with only possible codon for each amino acid, or you can do all possibilities using the notation I showed you in class to account for the wobble position of codons.

Now make your DNA double stranded by filling in the opposite DNA strand; label the 5’ and 3’ ends of this second strand and make sure you have an anti-parallel arrangement of DNA strands.

If you haven’t already, now consider the redundancy present on both strands, and make sure you have indicated sequences that account for all possible redundancies.

Realize that when a researched synthesizes a degenerate oligo that the final synthesis contains oligos with every substitution possible. The amount of degeneracy is defined by the number of different primer combinations in the mix. You can determine the degree of degeneracy by multiplying the number of changes present at each position together. If a position has no degeneracy then you multiple by 1 for that position.

Keep in mind that the trade-off between primer specificity and efficiency can be modified by altering the degeneracy of the primer. For example, the more degenerate the primers, the less specific annealing will be; however, decreased degeneracy will allow more potential to identify unknown variants. Anything over 1024 fold degeneracy is at the upper limit of potential usefulness.